Cushioning for packing cassette cases

ABSTRACT

[Problem] To provide a cushioning material that protects semiconductor wafers from an external impact when a cassette case is placed and packed in a cardboard box.  
     [Resolution Means] When a cassette case for wafers is placed in a cardboard box, a cushioning member is provided in a space with an internal wall of the cardboard box. The cushioning member includes an upper molded member and a lower molded member, which sandwich the cassette case from above and under to suspend the cassette case. The upper molded member and lower molded member have rectangular frame bodies that surround and fix a lid and a bottom surface of the cassette case respectively. A plurality of impact absorbing blocks that protrude toward the internal wall surface of the cardboard box, are disposed within a diameter width of the semiconductor wafers W in the cassette case when the main surface of the wafers W are viewed from front.

TECHNICAL FIELD

The present invention relates to a cushioning body for packing a cassette case, more specifically to a cushioning body for packing a cassette case that is formed of foamed material and is used when the cassette case having a substantially rectangular parallelepiped shape is placed and packed in a rectangular parallelepiped cardboard box.

BACKGROUND ART

Patent Document 1 is known as a conventional cushioning body for packing a cassette case of such a type. More specifically, the patent document discloses, as a cushioning body for transporting semiconductor wafers, a foamed polyethylene cushioning body, which is provided as a pair on upper and lower sides and is inserted between a container and an external box (rectangular parallelepiped cardboard box). The cushioning body is intended to protect a cassette case and semiconductor wafers from vibrations and shocks during transportation. The cushioning body provides a predetermined space between the external box and cassette case, and absorbs and reduces the above-described impact power by elastically deforming itself and the like.

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2005-41503

DISCLOSURE OF THE INVENTION Problems to Be Solved by the Invention

However, such a conventional cushioning body needs to be improved in points described below. Specifically, the conventional cushioning body is constructed with substantially rectangular frames on the upper and lower sides. On an external surface of the frames, two protrusions are provided on each of four side surfaces, such that the protrusions face an internal wall surface of the external box. Thus, a total of eight protrusions are provided on the upper and lower cushioning bodies, so as to provide a predetermined space with the external box. In this case, the protrusions on a side that faces a main surface of a plurality of semiconductor wafers loaded vertically in the cassette case, are provided in locations out of the main surface (i.e., not directly facing the main surface).

In a case where the external box is dropped with the main surface of the semiconductor wafers facing downward and the like, the impact force caused by the drop affects the cassette case and eventually the semiconductor wafers, through the cushioning body. Since the protrusions on the side facing the above-described main surface are provided in the locations out of the main surface, the protrusions cannot support the semiconductor wafers as both-end supporting beams. In addition, since the protrusions are provided substantially away from each other, a deflection and deformation amount in a central portion of the main surface of the semiconductor wafers is large, thus potentially causing cracks, scratches, splits of the semiconductor wafers.

The present invention is intended to provide a cushioning body for packing a cassette case that is used when the cassette case is placed and packed in a cardboard box and that protects semiconductor wafers in the cassette case from an external impact.

Means to Solve the Problem

The invention according to claim 1 provides a cushioning body for packing a cassette case provided between the cassette case and a box, when the cassette case having a box shape is placed and packed in the box having a rectangular parallelepiped shape, the cassette case being loaded therein with a plurality of semiconductor wafers having a main surface thereof standing substantially vertically. The cushioning body for packing the cassette case includes a lower molded member and an upper molded member. The lower molded member has a substantially rectangular frame body, fits to a bottom portion of the cassette case, contacts an internal bottom wall of the box, and supports the cassette case while having a space between an external wall of the cassette case and an internal wall of the box. The upper molded member has a substantially rectangular frame body, fits to a lid portion of the cassette case, contacts a ceiling wall of the box, and supports the cassette case while having a space between the external wall of the cassette case and the internal wall of the box. At least the upper molded member or lower molded member is provided with lateral impact absorbing blocks that protrude in an orthogonal direction to the main surface of the semiconductor wafers toward the internal wall of the box that faces the main surface. When a light is emitted in a perpendicular direction to the main surface of the semiconductor wafers loaded in the cassette case so as to project the lateral impact absorbing blocks, a projected image of the lateral impact absorbing blocks is positioned within a diameter width of the semiconductor wafers.

According to the invention described in claim 1, the lateral impact absorbing blocks provided on the upper molded member and lower molded member are disposed such that when the light is emitted in the orthogonal direction to the main surface of the semiconductor wafers in the cassette case so as to project the lateral impact absorbing blocks, the projected image thereof is positioned within the diameter width of the semiconductor wafers from a front view. Simultaneously, the lateral impact absorbing blocks are protruded perpendicular to the front and rear surfaces (main surface) of the semiconductor wafers in the above-described cassette case and toward the internal wall of the packing box. Thus, even when a large impact force is exerted on the box in the perpendicular direction to the main surface in such a case where the box tips over, the impact force is absorbed or reduced by the above-described lateral impact absorbing blocks, and thereby the impact force exerted on the semiconductor wafers in the cassette case can be reduced. In particular, the lateral impact absorbing blocks, which are provided such that the blocks are positioned within the diameter (width of the main surface) of the semiconductor wafers, can reduce the impact force that directly affects the main surface of the semiconductor wafers. Thereby, the lateral impact absorbing blocks protect all semiconductor wafers loaded in the cassette case. Thus, damage to the semiconductor wafers is reduced, and a split or crack is prevented.

The lateral impact absorbing blocks on both external surfaces of the upper molded member and lower molded member (external surfaces in parallel to the front and rear surfaces of the semiconductor wafers) do not need to be singularly provided on each surface. However, a plurality of blocks may be provided depending on a size of the cassette case. It is preferable that the lateral impact absorbing blocks be provided on each surface at a position opposed to a surface centering on the main surface of the semiconductor wafers (be provided on the both surfaces corresponding to the front and rear surfaces). When the plurality of blocks are provided on each surface, it is preferable that the respective lateral impact absorbing blocks be provided on symmetric positions of a vertical line (diameter) that passes the center of the semiconductor wafers in the cassette case from a front view of the main surface of the semiconductor wafers. By providing the lateral impact absorbing blocks as above, the semiconductor wafers can be evenly supported in the width direction thereof, and the external impact force can be absorbed and reduced to maximum.

In addition, the lateral impact absorbing blocks may be integrally molded with the above-described upper molded member and lower molded member. The lateral impact absorbing blocks may also be formed as separate bodies from the above-described lower molded member, by using a different material (material having a high impact absorbing capability, such as, for example, foamed plastics or rubber having a high elastic coefficient).

The invention according to claim 2 provides the cushioning body for packing the cassette case according to claim 1, wherein the substantially rectangular upper molded member is provided with four upper impact absorbing blocks on an upper surface thereof, the blocks protruding upward from apex positions of a square; and the substantially rectangular lower molded member is provided with four lower impact absorbing blocks on a lower surface thereof, the blocks protruding downward from apex positions of a square.

According to the invention described in claim 2, the vertical protrusions are provided on the upper molded member and lower molded member, thereby effectively protecting the cassette case against a vertical impact force.

The invention according to claim 3 provides the cushioning body for packing the cassette case according to claim 1 or 2, wherein two lateral impact absorbing blocks are provided on each of the upper molded member and lower molded member.

According to the invention described in claim 3, the four lateral impact absorbing blocks are provided, such that the blocks form a square within a square having a side of the diameter of the main surface of the semiconductor wafers in the cassette case from a front view. The lateral impact absorbing blocks thus can effectively reduce and absorb the impact force perpendicular to the main surface, thereby minimizing damage to the main surface. The structure supports the main surface at four positions.

Effects of the Invention

According to the invention of claim 1, even when a large impact force is exerted on the box on the side surface of the cassette case, particularly in the perpendicular direction to the main surface of the semiconductor wafers (direction in which a damage is most likely caused in semiconductor wafers), the impact force is absorbed by the above-described lateral impact absorbing blocks, thereby not directly affecting the semiconductor wafers in the cassette case. In particular, the lateral impact absorbing blocks are provided so as to be positioned within the main surface width of the semiconductor wafers. Compared to a case where the blocks are provided outside the diameter width of the semiconductor wafers, the blocks work more effectively to reduce the impact force to the semiconductors. Thereby, the lateral impact absorbing blocks protect all semiconductor wafers loaded in the cassette case.

In addition, according to the invention of claim 2, the protrusions provided on the upper molded member and lower molded member (upper impact absorbing blocks and lower impact absorbing blocks) can reduce and absorb the vertical impact force to the cassette case when the box is dropped. In particular, the blocks disposed at the apex positions of the square can evenly receive the vertical impact force at the respective protrusions, and thereby effectively reduce and absorb the impact force.

Further, according to the invention of claim 3, the semiconductor wafers in the cassette case can be effectively protected from the external force even in the most vulnerable direction.

BEST MODE OF EMBODIMENT OF THE INVENTION

A concrete embodiment of the present invention is explained below. FIGS. 1 to 10 illustrate the cushioning body for packaging the cassette case according to one embodiment of the present invention.

As shown in FIGS. 1 and 10, a box-shaped cassette case 10 is placed in a rectangular parallelepiped cardboard box 11 while being provided with a cushioning body in between, the cardboard box 11 being an external box. As shown in FIG. 10, the cushioning body includes a lower molded member 12, which is fitted to a bottom portion of the cassette case 10, and an upper molded member 13, which is fitted to a lid portion of the cassette case 10.

The cardboard box 11 has a rectangular parallelepiped shape having predetermined dimensions, in which one cassette case 10 compliant with the SEMI standard is placed and packed.

The cassette case 10 is a plastic box having a predetermined substantially rectangular parallelepiped shape, which includes a main body portion having a predetermine depth and a lid portion covering an upper opening thereof. Inside the main body portion, a plurality of silicon wafers W are loaded while being aligned in parallel. For example, 25 silicon wafers W having a diameter of 300 mm are placed into grooves in a vertical (perpendicular to the bottom surface of the cassette case) and parallel position in the cassette case 10. A direction in which the silicon wafers W are aligned is a long side direction of the cardboard box 11.

As shown in FIGS. 1 to 6, the lower molded member 12 is formed by molding foamed material, such as foamed polyethylene, foamed polypropylene, and the like. The lower molded member 12 has a frame body 21 having a rectangular shape provided with an opening at a central portion. The lower molded member 12 fits to the bottom portion of the above-described cassette case 10 while contacting the bottom surface thereof, and supports the cassette case 10 while having a predetermined space with an internal wall of the above-described box 11. More specifically, four corner portions of the rectangular (substantially # shaped) frame body 21 are provided with long-side direction blocks 23 and short-side direction blocks 24, which protrude externally within the plain surface. The long-side direction blocks 23 and the short-side direction blocks 24 contact the internal surface (vertical surface) of the box 11, thereby providing the predetermined space with the internal wall surface (vertical surface) in upper, lower, right, and left directions. In other words, the lateral impact absorbing blocks 23 and 24 have a square shape cross-sectionally, protrude from a predetermined position for a predetermined length, and have a flat vertical surface on an end portion of the protruding surface. The respective blocks 23 have a same shape and a same protruding length. As shown in FIG. 1, the blocks 23 protrude having a predetermined distance in between, such that the blocks are positioned within a width of a main surface, or a diameter width, of the semiconductor wafers W placed in the cassette case. In other words, two protrusions (blocks) 23 are provided on a front side of the cassette case 10 and two on a rear side. All the protrusions 23 are positioned within the width of the wafer diameter. FIGS. 1 and 2 indicate the positions of the blocks 23. All the respective short-side direction blocks 24 have a same shape and same dimensions.

The lower molded member 12 is further provided with four lower impact absorbing blocks 25 that are disposed at apexes of the square and protrude toward a lower side, so as to provide a predetermined space with an internal bottom surface of the cardboard box 11. Four lower impact absorbing blocks 25 are provided at the apexes of the square of the rectangular frame body 21 (corresponding to the bottom portion of the cassette case 10). The lower impact absorbing blocks 25 have a protruding height of 4.5 cm.

Meanwhile, as shown in FIGS. 7 to 10, the upper molded member 13, which constitutes the upper portion of the cushioning body, fits to the lid portion of the above-described cassette case 10 while contacting the upper surface thereof, similar to the lower molded member 12. At the same time, the upper molded member 13 supports the cassette case 10 while having a predetermined space with the internal wall of the above-described box 11. As shown in FIG. 7, the upper molded member 13 has a frame body 31 having a rectangular shape (substantially # shape) provided with an opening at a central portion. The rectangular opening is provided on an internal side of the frame body 31. The bottom surface of the cassette case 10 contacts the rectangular opening portion (a portion of the frame body) so as to be placed. Four corner portions of the rectangular frame body 31 are provided with short-side direction blocks 34 having a same size and protruding externally within the plain surface. The short-side direction blocks 34 contact the internal surface (vertical surface) of the box, thereby providing the predetermined space with the internal wall surface (vertical surface) of the box in upper, lower, right, and left directions. In other words, the blocks have a square shape cross-sectionally, protrude for a predetermined length, and have a flat vertical surface on an end portion of the protruding surface. The frame body 31 is further provided with a total of four long-side direction blocks 33, similar to the short-side direction blocks 34. The long-side direction blocks 33 have a square shape cross-sectionally and protrude for a same length perpendicular to the internal surface of the cardboard box 11, so as to provide a predetermined space between the internal surface and an external surface of the cassette case 10. With the long-side direction blocks 33 and the short-side direction blocks 34, the frame body 31 have a # shape from a plain view. On a top surface of the frame body 31, four protrusions 35 are further provided at apexes of the square of the frame body 31 (corresponding to the lid portion of the cassette case 10), as shown in FIG. 8. The protrusions 35 have a same square shape cross-sectionally and a same protruding height, which is set to 1.2 to 2.0 cm.

In addition, the two long sides of the frame body 21 of the lower molded member 12 are provided with the two protruding blocks 23 on each side having a predetermined distance in between as shown in FIG. 1. The blocks 23 are provided protruding such that when a light is emitted perpendicular to the main surface of the semiconductor wafers W, a projected location of a projected image of the blocks is positioned within the diameter width of the semiconductor wafers W in the above-described cassette case 10 when the main surface is viewed from a front surface. The four blocks 23 are provided in an orthogonal direction to the main surface (front and rear surfaces) of the above-described silicon wafers W from the lower molded member 12, and thereby constitute the lateral impact absorbing blocks protruding toward the internal wall surface of the cardboard box 11. The lateral impact absorbing blocks 23 contact the internal surface (vertical surface) of the cardboard box 11, thereby providing the predetermined space with the internal surface (vertical surface) of the cardboard box 11 in upper, lower, right, and left directions. The lateral impact absorbing blocks 23 have a flat vertical surface on an end portion of the protruding surface.

Further, the plurality of lower impact absorbing blocks 25 protruding toward the lower side of the lower molded member 12 provide the predetermined space with the bottom surface of the box 11. The lower impact absorbing blocks 25 are provided evenly at the four corner portions of the frame body 21 and have the same height. A protruding surface thereof is flat.

The upper molded member 13 and the lower molded member 12 are formed as an integrally molded plastics part using a mold and the like.

The cushioning body structured as above is placed in the cardboard box 11 as described below as shown in FIG. 10. The lower molded member 12 is first set. More specifically, the lower molded member 12 is inserted such that the lower impact absorbing blocks 25 contact the box bottom surface, and then the blocks 23 and 24 contact the box internal surface. Thereafter, the cassette case 10 that contains the semiconductor wafers is inserted from above to the lower molded member 12 and is placed such that the bottom surface of the cassette case fits into the recess space of the lower molded member. In this case, a plurality of (25) 300-mm silicon wafers W are placed in the cassette case 10 while being aligned in parallel and in the vertical direction so as to be perpendicular to the bottom surface of the cassette case. Then, the above-described upper molded member 13 is fitted to the upper lid surface of the cassette case 10.

The upper molded member 13 holds the upper end portion of the cassette case 10 in an internal square space of the frame body 31. The blocks 33 and 34 that protrude from the frame body 31 in a horizontal direction, provide a predetermined space with the internal wall surface (vertical surface) of the box 11. Further, the upper impact absorbing blocks 35 provide a predetermined space with the ceiling surface of the box 11.

In addition, the lower molded member 12 holds the lower end portion of the cassette case 10 in an internal square space of the frame body 21 from a plain view. The blocks 23 and 24 that protrude from the frame body 21 in the horizontal direction (lateral direction) provide a predetermined space with the internal wall surface (vertical surface) of the cardboard box 11. Further, the lower impact absorbing blocks 25 provide a predetermined space with the bottom surface of the cardboard box 11.

In this case, the long-side direction blocks 23 of the above-described lower molded member 12 are disposed so as to be perpendicular to the flat surface that includes the front and rear surfaces of the silicon wafers W in the above-described cassette case 10. Further, the long-side direction blocks 23 are provided protruding from the lower molded member 12 toward the box internal wall surface, such that when a perpendicular light is emitted to project the silicon wafer main surface, a projected image thereof is positioned within the main surface of the silicon wafers W from a front view.

When the cassette case 10 is placed into the cardboard box 11, the upper molded member 13 and the lower molded member 12 may be fitted to and combined with the cassette case 10, which may then be placed in the cardboard box 11.

Consequently, even when the cardboard box 11 tips over during transportation, the cushioning body, particularly the long-side direction blocks 23 of the lower molded member 12, can firmly support the cassette case 10 at the internal wall surface of the cardboard box 11, even though the cardboard box 11 is substantially bent and deformed, and can reduce and absorb the impact force. In this case, the respective blocks and the like absorb and reduce the impact simultaneously. Particularly, four long-side direction blocks (lateral impact absorbing blocks) 23 are provided on each of both the front and rear surface sides within the diameter width of the main surface of the silicon wafers W. Thus, the blocks 23 can reduce and absorb the impact force that exerts on the silicon wafers W, and thereby reduce the external force perpendicular to the main surface of the silicon wafers W. Thus, the damage to the silicon wafers W in the cassette case 10 is reduced, and a split or crack of the silicon wafers W is prevented.

As described above, when the cassette case 10 for storing and transporting the silicon wafers is placed in the cardboard box 11 for transportation, the cushioning body, which includes the lower molded member 12 and the upper molded member 13, is provided in the space with the internal wall of the cardboard box 11, so that the cassette case 10 does not directly contact the internal wall of the cardboard box 11. Thereby, the silicon wafers W can be effectively protected from the external impact. More specifically, the cassette case 10 is sandwiched from above and under by the upper molded member 13 and the lower molded member 12, which are the cushioning body formed of foamed material, so as to be held while being suspended. The upper molded member 13 and the lower molded member 12 have the rectangular frame bodies 21 and 31 that surround and fix the bottom portion and lid portion of the cassette case 10 respectively. Then, all the blocks (protrusions) provided on the lower molded member 12 and the upper molded member 13 prevent and protect the cardboard box 11 from being substantially deformed.

The following is a result report of a drop test in which the cushioning body for packaging the cassette case according to the present invention was used.

A plurality of upper molded members 13 and a plurality of lower molded members 12 were prepared. The plurality of upper molded members 13 had the upper impact absorbing blocks 35 having different protruding lengths (leg lengths), and the lower molded members 12 had the lower impact absorbing blocks 25 having different protruding lengths (leg lengths). The cassette case 10, in which 25 silicon wafers W were placed, was fitted into the upper and lower molded members above and under respectively, and then was packed in the cardboard box 11.

Then, the cardboard box 11 in which the cassette case 10 was packed was dropped from a predetermined height to a floor surface. It is then checked whether or not a crack occurred in the silicon wafers 25 in the cassette case 10. The drop test was performed in a case where the cardboard box 11 was dropped while the lid surface (top) of the cassette case 10 faced downward, and in a case where the cardboard box 11 was dropped while the bottom surface (bottom) of the cassette case 10 faced downward. Drop acceleration was also measured simultaneously. Table 1 below shows the results.

The leg length in the table indicates the protrusion length of the lower impact absorbing blocks 25 when the box was dropped with the bottom side down and the protrusion length of the upper impact absorbing blocks 35 when the box was dropped with the top side down. TABLE 1 Leg length G value during Drop direction (cm) drop Wafer crack Sample Bottom 5.0 61.2 Yes 1 Top 0.8 145.0 Yes Sample Bottom 4.5 70.3 No 2 Top 1.2 125.0 No Sample Bottom 4.0 75.2 Yes 3 Top 1.5 110.0 No Sample Bottom 3.5 79.4 Yes 4 Top 2.0 107.0 No

The above test results demonstrated that the silicon wafers W in the cassette case 10 did not crack, when the upper impact absorbing blocks 35 had a length of 1.2 cm to 2.0 cm. It was also demonstrated that the silicon wafers W in the cassette case 10 did not crack, when the lower impact absorbing blocks 25 had a length of 4.5 cm.

The above-described embodiment showed an example where the lateral impact absorbing blocks were provided on the lower molded member. However, the lateral impact absorbing blocks may also be provided on the upper molded member simultaneously. When two blocks are provided on each side (four on the both side surfaces) simultaneously, such that two lateral impact absorbing blocks on the upper molded member and two on the lower molded member form a square within the diameter width of the wafer main surface (four blocks on each side of the front and rear surfaces protect the semiconductor wafers), the semiconductor wafers are further effectively prevented from the impact force.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plain view illustrating a state where a cassette case is mounted according to a first embodiment of the present invention;

FIG. 2 is a plain view illustrating a lower molded member of a cushioning body according to the first embodiment of the present invention;

FIG. 3 is a front view of the lower molded member according to the first embodiment of the present invention;

FIG. 4 is a cross-sectional view along line D1-D2-D3-D4 in FIG. 2 of the lower molded member according to the first embodiment of the present invention;

FIG. 5 is a side surface view illustrating the lower molded member according to the first embodiment of the present invention;

FIG. 6 is a cross-sectional view along line C-C in FIG. 2 of the lower molded member according to the first embodiment of the present invention;

FIG. 7 is a plain view illustrating an upper molded member of the cushioning material according to the first embodiment of the present invention;

FIG. 8 is a cross-sectional view along line A-A in FIG. 7 of the upper molded member according to the first embodiment of the present invention and a side surface view illustrating the upper molded member;

FIG. 9 is a cross-sectional view along line B-B in FIG. 7 of the upper molded member according to the first embodiment of the present invention and a side surface view illustrating the upper molded member; and

FIG. 10 is an exploded view illustrating a layout of a cardboard box, the lower molded member, the cassette case, and the upper molded member according to the first embodiment of the present invention.

DESCRIPTION OF NUMERAL REFERENCES

-   11 Cardboard box -   12 Lower molded member -   13 Upper molded member -   10 Cassette case -   23 Long-side direction block (lateral impact absorbing block) -   25 Lower impact absorbing block -   35 Upper impact absorbing block 

1. A cushioning body for packing a cassette case provided between the cassette case and a box, when the cassette case having a box shape is placed and packed in the box having a rectangular parallelepiped shape, the cassette case being loaded therein with a plurality of semiconductor wafers having a main surface thereof standing substantially vertically, the cushioning body for packing the cassette case comprising: a lower molded member that has a substantially rectangular frame body, fits to a bottom portion of the cassette case, contacts an internal bottom wall of the box, and supports the cassette case while having a space between an external wall of the cassette case and an internal wall of the box; and an upper molded member that has a substantially rectangular frame body, fits to a lid portion of the cassette case, contacts a ceiling wall of the box, and supports the cassette case while having a space between the external wall of the cassette case and the internal wall of the box; wherein at least one of the upper molded member and lower molded member is provided with lateral impact absorbing blocks that protrude in an orthogonal direction to the main surface of the semiconductor wafers toward the internal wall of the box that faces the main surface; and when a light is emitted in a perpendicular direction to the main surface of the semiconductor wafers loaded in the cassette case so as to project the lateral impact absorbing blocks, a projected image of the lateral impact absorbing blocks is positioned within a diameter width of the semiconductor wafers.
 2. The cushioning body for packing the cassette case according to claim 1, wherein: the substantially rectangular upper molded member is provided with four upper impact absorbing blocks on an upper surface thereof, the blocks protruding upward from apex positions of a square; and the substantially rectangular lower molded member is provided with four lower impact absorbing blocks on a lower surface thereof, the blocks protruding downward from apex positions of a square.
 3. The cushioning body for packing the cassette case according to claim 1, wherein two lateral impact absorbing blocks are provided on each of the upper molded member and lower molded member.
 4. The cushioning body for packing the cassette case according to claim 2, wherein two lateral impact absorbing blocks are provided on each of the upper molded member and lower molded member. 